thank you for coming back to this issue.
I'm using a 560Ti currently.
It is good to hear, that you can confirm and resolve this bug.

However, as mentioned in the original post, I also had an issue, where my workaround of using a dummy fragment shader first (which should be more or less equal to your workaround) did not solve the issue.
Unfortunately, I'm too busy atm to test fully test it again.

Best